It used to be.
I know an English-born lady in her 90s who's spent most of her life in Australia and she uses the 3-syllables.
In one of the
Leslie Dunkling name books there's a quote from a British lady called
Irene - she explains that in the early 20th century an American musical was performed in London,and became a theatrical hit. It included a song about an
Irene. But the American composer had set the word
Irene to only two notes. The song caught on in England, and the 3-syllable pronunciation was doomed!